1. Field of the Invention
This invention relates generally to the field of aircraft instrumentation and more particularly to mechanical tools for a pilot's visual reference.
2. Background Information
The cockpit of an airplane is a very busy place and learning to fly an airplane requires the development of a complex skill set including aircraft handling and instrument interpretation. One of the many tasks to be performed by a pilot is to maintain the aircraft in a stable attitude during the many different phases of flight. The aircraft attitude is the position of the aircraft determined by the relationship between its three axes and a reference datum such as the horizon. Different phases of flight require different attitudes. For example, an aircraft is maintained at one particular angle with respect to the horizon is in order to maintain a steady climb. And, it may be maintained at a different attitude in level cruise flight and even still a further attitude in a descent. An emergency descent (requiring a steeper angle) is another attitude that must be maintained in those circumstances.
In fair weather conditions, known as VFR (Visual Flight Rules), both student pilots and experienced pilots alike refer to the horizon as a reference point, as does the body. A trick which is used by pilots of all levels and is taught early on in training is to choose a spot on the windshield (most times a dead bug) and line that spot up either with the horizon or at a particular distance from the horizon, (depending on the location of the dead bug) such as two inches below or two inches above, with reference to the actual horizon. This reference helps the pilot to maintain a stable attitude.
Some instrumentation heads-up displays have been designed, which are mounted adjacent the aircraft windshield to provide a display whereby the pilot can simply look straight at the windshield and have the display superimposed in front of him. Many of these devices superimpose an image in the windshield area by using a cathode ray tube or a prismatically projected image that requires certain lenses. This equipment can be very expensive. Such equipment also typically operates on the power supply system of the aircraft. Thus, such equipment could be rendered useless in a power loss during an aircraft's flight.
A mechanical heads-up attitude display was described in U.S. Pat. No. 3,706,970 which is a heads-up artificial horizon instrument that uses as its primary indicator a baton which is positioned in the field of view of a pilot and is coincident with the real horizon, very much the same way the artificial horizon works. The baton is supported from the end of a shaft, which is mounted in an instrument fixture. The instrument fixture includes a series of motors and gyroscopes that are turned and controlled by signals derived from the aircraft motion instruments and such that the baton is moved vertically within the field of view of the pilot.
The aforementioned device, however, is a heads-up attitude display that shows the actual position of the aircraft with respect to the horizon, much the same way the aircrafts instruments do. It does not provide the pilot with information based upon settings that are adjustable during flight, as phases of flight change, depending upon whether the pilot is in level flight, in a climb, in a descent, or attempting to hold an attitude in a banking position.
Furthermore, the heads-up indicator has instrumentation which is responsive to the rolling motions of the aircraft and include the signal producing gyroscopic attitude reference for controlling rotation of the shaft such that the horizon reference baton is continually coincident at all times with the real horizon. However, this signal producing gyroscopic attitude instrumentation can be quite expensive and complex and would most likely be fixed in a particular aircraft. Not only is it complex and thereby expensive, there is a further disadvantage in that many pilots fly rental aircraft and thus would need a tool that is readily removable and mountable in a different aircraft.
There remains a need, therefore, for a simple, mechanical device that can be used as a tool by a pilot for maintaining proper attitude in the various phases of flight at a glance in VFR conditions, while also maintaining his outside visual scan. There remains a further need for a device which is readily adjustable during flight and is simple to use, inexpensive and easily mounted in the pilot's field of view in the aircraft, but which is also removable for later use in a different aircraft.
It is thus an object of the present invention to provide a tool that gives a pilot a target towards which to aim the aircraft in order to achieve and maintain a desired airspeed or attitude in each of the various phases of flight, at the same time keeping his sight out the window as much as possible.